Motor control.



A. M. GOYLE. MOTOR CONTROL. APPLIGATION FILED JAN. 30, 1908.

Patented Nv.1,1910.

3 SHEETS-SHEET 1.

A. M. COYLE. MOTOR GONTROU.

AYPLIOATION FILED JAN. so, 190s.

Patelltd NOV. 1, 1910.

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Patented Nov. 1, 1910.

3 SHEETS-SHEET 3 0 2 w m I2 k u? W1 .l 1 L n .r la, N w f 7 Y n L f mq u.Y ,#0 Q r W M UNITED STATES PATENT OFFICE.

ANDREW M. COYLE, OF NEW YORK, N. Y., ASSIGNOR T0 OTIS ELEVATOR CQMPANY,0F JERSEY CITY, NEW JERSEY, A. CORPORATION OF NEW JERSEY.

MOTOR CONTROL.

Specification of Letters Patent.

.Patentes Nov. 1, 1910.

Application filed January 30, 1908. Serial No. 413,473.

To all whom 'it may concern:

Be it known that I, ANDREW M.- CoYLE, a citizen of the United States,residing in New York, in the county of New York and State of New York,have invented a new and useful Improvement iny Motor Controls, of whichthe following is a specification.

My invention relates to a system of control for electric motors,partlcularly those used for hoisting and lowering theater curtains, butit may have a' general application.

An object of my invention is the provision of improved means forcontrolling the speed of operation of the respective units of a multiplecurtain hoisting apparatus which lifts `and lowers curtains at the sametime. A further object is the provision of means for controlling theoperation of electric motors, wherein one mot-or is used for hoistingand another motor is used for lowering, also means for varying therelative speeds of the hoisting and lowering motors.

Other objects of my invention will appear hereinafter, the novelcombinations ofI elements being set forth in the appended claims.

In the accompanyingdrawings, Figure 1 represents a wiring diagram of mycontrol system, wherein a single motor is used for both hoisting andlowering; Fig. 2 is a wiring diagram in which there are two motors, onefor hoisting and one for lowering. Figs. 3 and 4 represent the hoistingapparatus adapted to the systems of control shown in Figs. 1 and 2respectively; Figs. 5 and 6 illustrate a preferred form of stopmotionapparatus shown'in 4-plan and side' views respectively.

Similar reference characters designate similar parts in both/figures.

The principal features of the particular form of'hoisting mechanism towhich my improved system of motor control is especially adapted aredisclosed in my co-pending application, Serial No. 397,310, tiledOctober 14, 1907 Patent No. 959,999, May .31, 1910, for an 4improvementin 'curtain hoisting apparatus.

Briefiy described, the hoisting apparatus to which .my invention isparticularly' adapted, is illustrated in Figs. 3 and 4, and

comprises a motor 80 upon whose shaft 93 is secured, at regularintervalswa series of friction driving members ork ditks, such as 94adapted to coperate with jother frictional driven members, such as 95,which latter aregeared to suitable hoisting drums as 96. Each frictiondriving disk and cooperating driven mechanism and hoisting drumcomprises a single unit of a multiple hoisting apparatus. While thenumber of such units may be as many as desired, for purposes ofillustration I show in Figs. 1 and 2 of the present drawings controllingsystems for a 4multiple hoisting apparatus having six hoisting drums orunits, and adapted to control the hoisting and lowering of siXl theatercurtains or other apparatus. The friction wheels 94 and 95 which aregeared to their respective hoisting drums, are pivotally mounted so thatthey may be independently raised out of or lowered into engagement withtheir respective friction driving disks upon the motor shaft. Eachhoisting unit is provided with a brake shoe 99 which coperates with thefriction wheel 95 driven by the disk 94 upon the mo-l tor shaft, andthis brakek shoe is so arranged that thebrake is applied and thefriction wheel is raised out of engagement with the driving meanssimultaneously. This operation is effected by means of a separate `thatwhen the same is properly ener ized and the brake magnet is alsoenergizel the parts are in proper position to effect a raising of theload. If, however, the brake magnet is energized and the tripping magnetis denergized or does not receive current, the brake will be released,but the tripping apparatus controlled by the tripping magnet Willprevent the friction driving wheel from engagin the driving disk `uponthe motor shaft, an the hoisting drum is in a position to be turnedbackward by means -of the unbalanced load. f The apparatus to which thecontrolling system shown in Fig. 1 is especially applicable has,furthermore, a number of gear wheels such as g 100; one foreach hoistingunit, each'of which is gearedl directly t-o its'` respective hoisting4drum and which is connected through a clutch mechanism to a sprocketwheel 101 which in turn is connected by a sprocket cha-in 102 to asmaller sprocket wheel 103 rigidly mounted upon the motor 5 shaft. Thisclutch mechanism is so arranged that when the hoisting drum is raising aload, or when the brake is applied and the drum at'rest, it does notcome into operation, but as soon as the unbalanced load tends to drivethe hoisting drum backward, the clutch at once operates and operativelyconnects the hoisting drum to the motor shaft and the speed of descentof the load depends upon the speed of rotation of the motor. Thus, whilethe motor always runs in one direction, the speeds of hoisting andlowering are both dependent upon the motor speed.

The apparatus particularly adapted to the controlling system shown inFig. 2, is illustrated in Fig. 4 and is similar in every respect to theforegoing description, but with this one exception: The gear 100 meshingwith the hoisting drum and connected through a clutch mechanism to thehoisting motor, is in this instance designated by 100 and is connectedthrough a similar clutch mechanism to the shaft 93 of an additionalmotor 80 which is only used for lowering. Each motor therefore, performsits separate function ofl hoisting and lowering, and as the relativespeeds of these motors may be varied at will, the relative speeds ofhoisting and lowering may be adjusted to any desired speed, and thus, inthe particular case of theater curtain control, manyand varied sceniceffects may readily be produced with facility and despatch.

Each hoisting drum is provided with a limit switch or stop -motionapparatus which is operated by the hoisting drum through gearing andserves automatically toy slow down and stop any of the hoisting drums ateither the upper or lower limit of curtain travel. g

The stop-motion apparatus maybe mounted in a housing 104 onftop of themachine and operated by gear wheels 105 respectively in mesh with thegear wheels 106 of the hoisting units. The purpose of the stop-mo` tionapparatus is to operate circuit-breakers so as to denergize theelectro-magnet 62, and to also slow down the motor a short time l priorto the denergization of the brake electro-magnet. It is to be understoodthat for each unit of the' multiple hoisting apparatus there is acorresponding unit of the stop-motion apparatus, and that when astop-motion unit operates to open its circuitcloser only thecorresponding unit of the multiple hoisting apparatus will be effected.This operation is automatic, as will be more fully explainedhereinafter.

Referring now more particularly to Figs. 5 and 6 where is shown apreferred form of my improved stop-motion apparatus adapted to ahoisting machine having any desired number of units, it will be seenthat I have provided a base 107 for the stop-motion apparatus, whichbase may be bolted to the frame 108 of the hoisting apparatus shown inFigs. 3 and 4. A rectangular frame 109 is secured to the base 107 andprojecting upwardly from its opposite rear corners are integral bracketarms or bearing standards 110 and 110 which support a rod 111 upon whichare loosely mounted swinging arms 112 and 112. Between these arms is abushing 113 on the rod 111; the purpose of said bushing being to holdthe arms 112 and 112 8O spaced apart and in their proper positions. Thegear wheel 105 which is driven by the gear 106 of a hoisting unit issecured to a shaft 114 which carries a small pinion 115. The latterextends the entire length of the shaft 114. Mounted on the frame 109 andparallel with the shaft 114 is a screw threaded shaft 116 which is heldstationary by its supports. Mounted on the shaft 116 are two gear wheels117 and 117 whose hubs are 90 screw-threaded to correspond with thethreads on the shaft 116. On the hub of the gear wheel 117 are two cams11S and 119, and on the hub of the gear wheel 117 are two similar cams118 and 119. A rock- 95 shaft 120 is journaled on the base 107 andrigidly secured thereto are rock-arms 121 and 122 which have at theirouter extremities lateral projections 121 and 122 respectively, whichare arranged to be engaged hy the cams 118 and 118, respectively. Thecams 119 and 119 are arranged to engage the detents or trips 123 whichare carried by the arms 112 and 112; the latter each carry bridgingmembers 57 and 58 to electrically 105 connect the contacts 59 and 61.

The operation of the construction shown in Figs. 5 and 6 is as follows:Vhen the hoisting mechanism shown in Figs. 3 and 4 is in operation, thegear wheels 117 and 117 110 of the stopmotion device are rotated bymeans of the gear connections above described. This rotation will impartto the gears 117 and 117 alateral movement, owing to their threadedengagement with the shaft 116. If it be assumed that the gear wheel 117is rotated in a counter-clockwise direc- `tion when looking at it fromthe right, then l contact plate 57 and breaking the electrical engagedconnection between the contacts 59 and 59.

It will be observed that the lateral surfaces of the cams 118 and 119are inclined or spiral in form and of the same pitch as the threads onthe shaft 116. This is` for the purpose of preventing any lateralA orside thrust of the cams against the parts they engage. This inclinationof the cams corresponds to the pitch of the threads on the shaft 116, sothat the forward movement of the cam 119,-for example, as it approachesthe lug 123, is just equal "to the receding movement due to the inclinedsurface of the cam, and the lug 123 will therefore not be until the endvof the cam rides under it, lifting the arm 112. The slow-down switch 46is arranged to be operated by the rotation of the rock-shaft 120 everytime one of the hoisting drums approaches its limit of movement ineither direction.

Referring to Fig. 1, 80 designates the motor which is usedffor bothhoisting and lowering, and which always runs in' one direction. Themotor receives current from the positive and negative mains (designatedand respectively) connected to a suitable source of current supply. 1and 2 are the magnets which operate, when energized, to close a circuitto the motor 80. 8, 9, 10 and 11 are sections of the motor startingresistance, which sections are controlled by the electro-magnets l12,13, 14 and 15, re-v is the fast speedmagnet, and 29 is a magnet' whichoperates to prevent the brake being raised when the motor 80 is at rest.The switch 45 is for the purpose of rendering the speedA controllingswitch 33 inoperative whenever desired. 62, 62', etc., designate brakemagnets for the various hoisting units, while 63, 63, etc., are theCQrresponding trip magnets. .57 and 58 are the mechanically operatedlimit stops, 57 being the up limit and 58 the down limit for a singleunit: The other units have similar limit. switches, sis/57', 58, etc. 64and 65 each designate a series of selective push-buttons, six up buttonsand sixy down buttons, and all of these buttons are what are known asself-holding buttons, in that when pressed they are held.

in this position against the action of a spring or equivalent means byan electro-magnet. In the system shown there are six up buttons and sixdown buttons, and the operation of these buttons determines theparticular hoisting unit which is to be operated either to raise orlower its load, depending uponl the particular button operated.

The operation of the system of electrical control is as follows Any oneof the buttons 64 or 65, or more than one, may be pushed, but for thepurpose of illustration we will assume that the right hand button 65 ispushed against the action of the spring 66. It will be observed that theupper magnet windings 69, etc., of both the up and down buttons are allconnected in series, and, furthermore, they are directly connected bythe wire 60 to the main, and are also connected through the normallyclosed contacts 55 directly to the -j main. These pushbutton magnetcoils therefore receive current directly from the main line through thecontacts 55 and are thus energized, and, while the magnet coil of anyone button is not of sufficient strength to automatically operate thepush-button, it has the necessary power to hold the push-button inclosed position after the same has been manually pushed. This buttonhaving been pushed,

the contacts 72 are brought into electrical4 engagement with eachotherand are held in this positionagainst the action of the spring 66. Thehoisting drum corresponding to the button just operated is now in properrelation to hoist its load. The next operation is to move the lever 34of the manually operated speed switch 33 to the right until the switchlever 34 electrically connects the fixed segmental contacts 43, 42 and35, the position of slow speed. This operation closes a circuit which isas follows From the main at the junction point 7 7 to and through themagnet 1, wire 81, magnet coil 2, magnet coils 29 and 31, wirev 82,contact 42, switch lever 34, contact 43, switch 45, and by wire 6() tothe main at the junction 79. A parallel circuit is also closed 'atY thesame time from the contact 42, switch lever 34, contact 35, contact 51,the bridging contact 50, and by the wire 83, to the main at the junction78. By thus closing a circuit through the magnet coils 1, 2, 29 and 31in Series, the same become energized and operate to close the contactsassociated therewith, namely, tliecontacts 6, 7, 30 and 32,respectively. A circuit is now closed to the motor armature through thecontacts 6 and 7 including the sectional starting resistances 8, 9, 10and 11. At the same time a circuit is closed to the motor field winding4, this circuit being from the -lmain at the junction 84, magnet winding54, motor.lield 4, wire 85, contacts 32, wire 86, and so to the main byway of contacts 7. The motor 80is now enabled to start, the currentflowino' to the armature being limited by the sectional startingresistances 8, 9, 10 and 11 in series therewith. Upon closing thecontacts 6 and 7 a circuit is established through the 'slow-down limitswitch 46 and the magnet coil 48, and the latter becomes energized toraise the contact plate 52 into electrical engagement with thestationary contacts 53, also the contact plate 50 out of engagement withthe fixed contacts 49 and 51. circuit vbefore mentioned through themagnet coils l, 2, 29 and 31 from the contact 42, switch lever 34,contacts 51, 50, and wire 83 to the main. The circuit to these magnetsremains completed, however, through the contacts 42 and 43 as beforepointed out.

The magnets 26, 27 and 28 are connected in series, and at this time areconnected across the motor armature, the circuit being as follows :-Fromthe motor brush 3, wire 87 and normally closed contacts 56, through themagnets 28, 27 and 26 to the contact 35 of switch 33, contact 43, switch45, wire 60, contacts 7 to the motor brush 3. At the moment of startingthe motor from a position of rest,

the voltage across the motor brushes 3 and 3 is at a minimum, whichvoltage increases as the motor increases in speed, due to the C. E. M.F. of the revolving armature, and,

Vsince the magnets 26, 27 and 28 are connected across the motor brushes,the current flowing in these magnets is proportional to the brushvoltage of the motor. If the` motor is heavily loaded upon starting, thevoltage across the armature brushes Ywill remain relatively low, due tothe fact that the motor will run at a low speed with consequent low C.E. M. F., the greater part of the drop of potential taking place acrossthe starting resistances 8, 9, 10 and 11. With the present conditions,however, since but a single unit is hoisting, the load is comparativelylight and the voltage across the motor armature soon rises to a pointsufliciently great to effect the operation of the magnets 26, 27 and 28.The operation of the magnet 28 closes the contacts 25, which connectsthe resistances 20, 21 and 22 in parallel to the motor armature. Themagnet 27 operates to shortcircuit the resistance 22, leaving theresistances 20 and 21 in parallel to the armature; while the magnet 26short-circuits the resistance 21, thereby leaving'the resistance 20alone across the armature, and under no conditions in this resistance 20ever short-circuited. The conditions at this time are for slowest speed,that is, the resistance in series with the motor armature is at amaximum, the field strength is also at a maximum, and the resistance inparallel with the armature is at a minimum.

At substantially the same time that the motor receives current by theoperation of the magnets 1 and 2, the magnet 29y which is included inthe circuit of these magnets closes a circuit from the main through Thisopens the parallelV ing the push-button in operative position.y

The brake magnet and tripping magnet being both energized at this time,the hoisting apparatus is in properV condition to eifect the raising ofthe load as before pointed out. The magnet 54, it will be remembered, isincluded in the circuit of the motor eld winding 4, and the same currentpasses through both. Since the current in the motor ield 4 does notinstantaneously rise toits full value as soon as its circuit is closed,due to the selfinduction of the field winding, the magnet 54 does notimmediately operate to separate the contacts 55 -and thus break thecircuit through the upper magnet windings 69 of the series of pushbuttons. This arrangement insures that the lower magnet winding 71 ofthe operated push-buttons will become fully energized by the operationof the magnet 29 before the magnet 54 has operated to open the circuitof the upper push-button windings, and the push-button remains in itsoperative or closed position.

The switch lever 34 is next moved until it passes onto contact 36 and oof contact 35. The circuit to the magnet 26 -is now opened at thecontact 35, but the circuit to the magnets 27 and 28 is still closedthrough the contact 36. The magnet 26 therefore becomes denergized andopens the contacts 23, inserting the resistance 21 in the parallelcircuit to the motor armature. This increase in resistance across thearmature circuit results in an increase in motor` speed. Upon furthermovement of the switch arm 34 onto contact 37, the circuit to the magnet'27. is opened at the contact 36, while the magnet 28 alone remainsenergized. The circuit across the armature now includes the resistances20, 21 and 22 andthe motol` further increases its speed. The lever 34isnow moved onto contact 38 and oi of contact 37. This opens the circuitto the magnet 28 at,y the contact 37, causing the same to open itscontacts and thereby opening' the parallel circuit to the armature atthe contacts 25 and themotor further increases its speed. Since theswitch arm 34 now rests upon the contact 38, the magnet 12 includingthe'resistance 74 is connected across the motor armature, this circuitbeing traced as follows :-From the motor brush 3, wire 87, contacts 53(these latter being in electrical engagement with each other/at thistime), through the magnet winding 12, wire 68, resistance 74, contacts38 and 43, switch 45, wire 60, contacts 7, and to the armature brush 3.l The magnet 12 now receives curl a short circuit across the sectionalstarting resistance 8. The motor now runs still faster with but one-halfof the starting resistance in circuit.'

When the magnet 13 operated to close the contacts 17, the'contacts 56were separated at substantially the same time, thus preventing anypossible circuit to the magnets 26, 27 and 28 through the wire 70 aslong as the magnet 13 is energized. The switch arm 34 next moves ontocontact 40, thereby energizing the magnet 14 through the resistance 76,thereby cutting out or short-circuiting the sectional resistance 10. Theswitch arm is now moved onto contact 41 which completes a circuitthrough the magnet 15 which operates to short-circuit the' remainingstarting resistance 11. The ohmic resistance of each of lthe resistances74, 7 5 land 76 is so proportioned that the current strength in any oneof the magnets 12, 13, 14 or 15 is the same for the same motor potentialwhether one magnet alone is in circuit or all of the magnets; that is tosay, the ohmicvresistance ot the resistance 74 is equivalent to threetimes that of any one of these magnets, that of the resistance 75 totwice the mao'net resistance, while that of resistance 76 is the same asthe resistance of one of the magnets. These magnets 12, 13, 14 and 15are preferably so arranged that should the switch arm 34 be rapidlymoved from its initial position to the contact 41, the magnets willrespond to the rise of motor potential as the same speeds up and willoperate successively in prearranged order so as tofsh'ort-circuit thesectional starting resistances in proper order. This may be accomplishedin one of several ways well known in the art and needs lno furtherdescription. The motor now receives current at full line potential withmaximum field strength and assumes a speed to correspond therewith. Theswitch arm is next moved until it rests upon the segmental contacts 4l,44 and 43. The circuit to the magnets 12, 13, 14 and 15 remainsunbroken, but a circuit to the magnet 31 isopened through the wire 82 atthe contact 42. The circuit including the magnet 29 is not interrupted,however, since an additional circuit is closed through the contact 44and resistance 73, which resistance is now substituted for the magnet31. The magnet 31 nowbecomes denergized and the contacts 32 controlledthereby move out of electrical engagement with each other. This resultsin placing the resistance 5 in series with the motor field winding 4,since the short-circuit heretofore maintained across the resistance 5 bythe contacts 32 and wires 85 and 86 is now opened through the separatingof these contacts. By thus inserting the resistance 5 into the motorfield circuit, the cur- Y rent flow in the latter is reduced, the fieldstrength is therefore weakened, and the motor and connected hoistingunit run at full speed. As the load carried by this hoisting unitapproaches its upper limit of travel, the mechanically operatedslow-down switch 46 which is operated every time one of the hoistingdrums approaches its limit of movement in either direction, opens thecircuit to the magnet 48 at the contacts 47. This magnet at once becomesdenergized, causing the contact plate 52 to move out of engagement withthe contacts 53, and the Contact plate 50 to electrically engage thecontacts 49 and 51. This operation opens the circuit to thema ets 12,13,- 14 and 15 at theV contacts 53 an 'the entire starting resistance isre-inserted into the armature circuit, while the contacts 56 are oncemore placed in electrical contact .with each other. The denergization ofthe magnet 48 also connects the contacts 49, 50 and 51 together, therebyclosing two circuits, one of which is from the motor brush 3, wire 87,contacts 56, wire 7 O, magnets 28, 27 and 26, wire 91, contacts 51 and50, wires 83 and 92, contacts 7, to the motor brush 3'; the othercircuit is from the right-hand terminal of the motor field winding,wires 85 and 90, contacts 49 and 50, wires 83 and 9,2, to the main. Thefirst-named circuit effects the operation of the magnets 26, 27 and 28which will operate to connect the resistance 20 across the armature. Thesecond-named circuit effects the shortcircuiting of the resistance 5,both terminals of which are now connected to the main and the motorfield Y,strength is again at a maximum. The effect of these operationsis to slow the motor down to extreme slow speed. The hoisting unit hasat this time raised the -load tol its upper limit and the mechanicallyoperated limit switch 57 automaticallyoperates to open the circuitthrough the'brake magnet 62, tripping magnet 63, and push -button magnet71. The hoisting drum of the unit corresponding to the push-buttonoperated now comes to rest and the spring 66 returns the button to itsinitial position as shown on the drawing. The motor continues to run,however, at reduced speed until the slow-down mechanism operates toelectrically connect the contacts 47, thereupon the magnet 48 1s '1'30established to the magnets 12, 13, 14 and 15 and the circuit through themagnets 26, 27 and 28 is opened, while the short-circuit around thefield resistance is removed and the motor automatically runs up to fullspeed.

Should it be desired to operate two or more hoisting units at t-he sametime, the push-buttons corresponding to the desired hoisting units maybe pressed, after which the motor is started and run up to speed by theswitch 33. The slow-down switch 16 operates automatically to slow themotor as any one of the hoisting units nears its limit of travel,afterwhich the limit stop corresponding to such hoisting unit which hasreached its limit of travel operates to bring such unit to rest. Theslow-down switch again operates so as to speed up the motor, and, asanother hoisting unit nears its limit of travel, the motor is againautomatically slowed down until such hoisting unit reaches its limit oftravel and the same is brought to rest, after which the motor againspeeds up. This operation continues as long as there are any hoistingunits operatively connected to the driving motor.

When it is required that any oneor more hoisting units shall operate tolower their load, the corresponding down buttons are pushed. The variousoperations of different parts are similar to the operations alreadydescribed in connection with raising one or more loads, with thiseXceptiom-when a down button is operated and the switch 33 is moved soas to start the motor, the circuit closed through the lower magnetwinding of the push-button includes the magnet winding of thecorresponding brake and down limit switch, but does not include thecorresponding tripping magnet and the latter is not energized,consequently, while the brake will be released, the tripping mechanismwill not ermit the hoisting drum to be operative y connected to thefriction driving disk on the motor shaft. The unbalanced load will,however, since the brake is released, cause the hoisting drum to turnbackward, thereupon operatively connecting the hoisting drum through itscorresponding clutch mechanism and sprocket to the cooperating sprocketmounted upon the motor shaft, and in this manner the lowering, as wellas the raising, of the load is dependent upon the motor speed which maybe varied within wide limits by means of the manually operated switch33.

rlhe operation of the slow-down and limit devices is similar,.whetherthe load is being raised or lowered, and while a single switch is usedto controll the slowing down of the motor, whether the same is hoistingor lowering, aseparate limit switch is used for the up and down motions.It is not necessary first to operate the push-buttons aQnd then startand accelerate the motor, but, if desired, the motor may be started andrun at any desired speed within the capacity of the machine, and thenany desired up or down button may be pressed, the hoisting unitcorresponding thereto will raise or lower its load and automaticallyslow down, and inally stop at its limit of travel.

In the system of electrical control just described where the differenthoisting units ar'e hoisting and lowering at the same time, it is notpossible to change the speed of hoisting without changing the speed oflowering as well. The system of electrical circuits illustrated in Fig.2, in which two motors are used, one for hoisting and one for lowering,makes it possible to vary the hoisting or lowering speeds at willindependently of each other.

Referring to Fig. 2, 80. designates the hoisting motor and 80 thelowering motor. The motor 80 is preferably of greater power than that ofmotor 80', for the reason that the unbalanced load upon any hoistingunit, when the same is operating to raise or lower its load, has to beraised against gravity in the case of hoisting, but assists the loweringmotor .80 when it is being lowered.V In actual practice it is found thatthe motor 80 is driven by thennbalanced descending load, and thus themotor acts as a generator, sending current back into the line andthereby providing an electro-dynamic brake of variable retardation.

The operation of the electrical system of control is substantially thesame in Fig. 2 as in Fig. l. It will be noticed that the startingresistance for the hoisting motor 80 comprises tive sections controlledby five magnets 12, 13, 14, 15 and 15', also the armature parallelresistance has but two sections controlled by a corresponding number ofmagnets 26 and 27. The speed ofthis motor 80 is controlled by the switch33 in a manner similar to that pointed out in connection with Fig. 1.The up limit switches 57, 57, etc., and the down-limit switches 58, 58,etc., operate in like manner to bring any particular hoisting unit ornumber of units to rest as soon as each individual hoisting unit hasreached its limit of travel. The same main line switch 93 suppliescurrent to both motor controlling systems from a suitable source ofelectrical supply indicated by the and signs. It will be further noticedthat in Fig. 2 there is no slow-down magnet for the hoisting motor. Aslowdown magnet is, however, provided for the lowering motor 80 and isoperatedautomatically by the slow-down switches4 46, 46, etc., wheneverany one of the hoisting units has operated to lower its load by means ofthe motor 80 almost to its lower limit of travel, shortly after whichthe corresponding limit switch comes into action and brings the load torest. The motor 80 is immediately'speeded up automatically until anothercurtam approacheslits lower limit of travel and the same cycle ofoperations is repeated as long as there are any hoisting units activelyengaged in lowering. The speed of the hoisting and lowering motors 80and 80 is controlled independently controlling switches 33 and 33,respectively. In this manner when the hoisting apparatus is used tooperate theaterI curtains, certain curtains may be rapidly raisedv whileat the same time other curtains may slowly descend, or the Jreverse maybe the case, and in this manner many -beautiful scenic effects mabewproduced at will: The slowing down an consequent stopping of all ofthe curtains upon reaching their. limitv of travel is accm lishedautomatically.

' Whi e I have illustrated and described the preferred 'form of myinvention, I do not wish to be limited to the precise construction andarrangement of parts shown,`since it is obvious that various changescould readily be made in the constructlon and arrangement of parts bylthose skilled in the art without departing from the spirit and scope ofmy invention.

What I claim as new and desire to protect by Letters Patent of theUnited States is 1. In a system of electrical control, the combinationwithv a source of current supl ply, of an electric, motor, controlling'devices'for the motor, a plurality of electromagnets, and selectivedevices operative respectively to effect the energization of one or bothof said electro-magnets.

2. In a system of electrical control, the combination with a source ofcurrent supply, of an electric motor, motor controlling l `nrechanism',a brake magnet, a` trip magnet,

andgmeans for effecting the energlzation of either the brakemagnet aloneor both the brakemagnet and trip magnet when current 3. In a system ofelectrical control, `the Acombination with Aa motor, of a source of-current sup ly, motor controlling mechanism, a-pllira ity ofelectro-magnets, and. de- Vices -for effecting the energization of said'magnets when current isv supplied to the motor, one of saiddevicescontrolling one of said magnetsand the other of said devicescontrolling both of said magnets.

'4. In a system of eleb 'cal "control,the

l combination with a source f current supply, -of an electric motor,controlling mechanism for. the motor, a brake magnet coil, a trip y,bsma'gnet coil, a circuit for the brake magnet l K therefor, a brakemagnet coil, a tripmagnet coil, circuits for said coils each open at aplurality of points, selective devices for manually closingeach'circu/it at one point, and means for automatically com leting saidcircuits when current is supp ied to the motor.

6. In a system of electrical control, the combination with a source ofcurrent supply, of an electric motor, controllin mec anism therefor, abrake magnet coi a circuit therefor normally open at a plurality ofpoints, a manual device for closlng the circuit at one point, and meansfor automatically completing said circuit when current is supplied tothe motor.

7. In an electrical System of control, the combination with a source ofcurrent supply, of an electric motor, a manual con= trolling switchtherefor, a brake magnet coil, a manually operable switch in the circuitof said coil, an electro-magnetic switch in said circuit, and means foroperating said `electro-.magnetic switch when the controlling switch forthe motor is operated.

8. In an electrical system of control, the combination with a source ofcurrent supply, of a motor, controlling ineans therefor, a plurality ofbrake magnet coils, atrip magnet coil associated with each brake magnetcoil, selective devices controlling the circuits of the brake magnetcoils alone,-and selective devices controlling the circuits of the brakeand trip coils together.

9. In a system of electrical control, the combination with a motor, ofcontrolling apparatus therefor, a bank of pushbutton switches comprisinga double series of electro-magnets, a series of devices controlled bysaid switches, a normally closed circuit for one series of saidelectro-magnets, means for opening said circuit when the motor circuitsare closed, an additional circuit for said second series ofelectro-'magnets open when the motor circuits are open, and means forclosing saidY second circuity when the motor circuits are closed.

In testimony whereof, I have signed my name to this specification in,the presence of t`wo subscribing witnesses.

f ANDREW M. COYLE. Witnesses:

' ,SAMUEL D. CoLLErr,

ANNA-ASHT0N.

